Engine starter



` ENGINE STARTER Filed Feb. 6, 1922 "/af. A

R. ABELL 1,778,010

25 movementy or torque.

Patented Oct. 1.4, 1930 UNITED STATES ROLLIN ABELL, OF'MILTON, MASSACHUSETTS ENGINE STARTER Application led February 6, 1922. Serial No. 534,355.

. This invention relates to starters for 'internal combustion engines, and, among its objects are the following: to provide an improved eonstruction by which the load will be applied to the starting motor gradually so as to avoid sudden shock; by which the shiftable starting pinion will be shifted into gear automatically .before the starting motor can accelerate appreciably; by which the shifting movement of the starting pinion will be Vmade initially slow but rapidly accelerative; and by which the end-thrust applied to the starting pinion will be diminished gradually as the pinion moves from its inoperative to its operative position.

These objects cannot be attained with starters of the nut-and-screw type (which is the only automatic type heretofore recognize'd as possessing commercial merit) because cooperative screw-threads are restricted to a uniform lead or pitch, of whatever steepness, throughout their range of action, andare therefore incapable of developing variations in end-thrust, speed of axial These three factors, therefore, -must remain constant in a starter of the nut-and-screw type, unless some supplemental device is provided to modify the effects of the screw-threads.

The accompanying drawing illustrates an embodiment of the invention comprising a cam arranged to shift the pinion into gear but not out of gear, a light spring being provided to shift the pinion out of gear at the moment of engine pick-up. This cam, by reason of certa-in peculiarities of shape, develops initially slow but powerful axial movement and no appreciable torque, thus shifting the pinion into meshed relation Without turning it. Successive stages of the cam develop torque gradually but rapidly, the effective surface of the cam having a relatively slight pitch at one portion to shift the pinion into meshing position, and a gradual increase of steepness to a degree Within the angle of repose, thus loading the starting motor without shock and before it has accelerated to maximum speed. An advantage of the invention, according `to the il- 50 lustrated form of cam, is that it forms finally a positive transmissiony the positive qualit of which is developed gradually, and there ore without shock, during the pinionshifting operation. For mechanical reasons this cam is preferably ofl duplex or twin form, having two simultaneously operative cam surfaces of the same form and effect a'r rangedl diametrically opposite each other. Vith .the construction shown all the afore-l said effects' may be brought about in less than one half of the first rotation of the starting motor, whereas commercial starters of the screw-thread type require at least one and one-half rotations to establish a starting condition. When the rapidity of acceleration of an electric starting motor is considered, and when the aforesaid features of my present construction are taken into such consideration the advantages of such construction become significant.

In addition to possessing thefeatures hereinbefore mentioned the illustrated construction is simpler, more durable and more reliable than any heretofore offered to the trade.v

Referring to the drawings,

Figure 1 is an elevation showing the starter in its normal or initial condition, and includes a fragment of a gear such as the fly# wheel gear of an internal combustion engine.

Figure 2 is a similarl view excepting that the starter is in its operative condition and is represented partly in section. 4

Figure 3 is a diagrammatic view including a development of the operating cam.

The following description, in so far as it deals with details of construction, is descriptive merely of the illustrated form of device, and is not to be regarded asimposing any limitations on the scope of protection more broadly defined in the appended claims.

The rotatable shaft 10, journaled in the bearing 11, may be the rotor shaft of an electric starting motor, and the bearing 11 may be formed in the casing of such motor.

The casing would, as usual, provide two bear- 4 ings for the shaft. For purposes of definition the shaft may be regarded as an element of the rotary operating unit hereinafter referred to. Any preferred means may be provided to prevent axial movement of the operating unit.

A rotary and axially movable transmission unit surrounds the smooth cylindric outboard portion 12 of the shaft so as to slide thereon and be supported thereby. This transmission'unitcomprises-a sleeve 131,011 Which are formed teeth to provide a starting Vpinion 14 for transmitting rotation to the gear 15. lTheV latter is represented as `a ily-Wheel gear of an internal combustion engine. A. light compression spring 16 surrounds the shaft and is sufficient to move the transmission unit to its normal or initial position as shown by Figure 1. No other force is brought' into play for this purpose.

The axial movement necessary to shift the starting 'pinion to operative position, shown byFig'ure 2, vis lbrought about by tWin cams 20 ofthe open crown type and twin studs 21.

For manufacturing reasons and to use the factor of inertia most advantageously l prefer to form the cams on the transmission unit and to Vfix the studs to the shaft so that they will be elements of the operating unit. Furthermore, I prefer to give the sleeve a relatively large diameter in that portion that provides the cam surfaces. The studs may be the `end portions of a single piece of rod pressed rtightly into a hole extending diametrically through the shaft.

To minimize the lateral strain on the starting shaft 10 developed by the pinion 14 and geary 15 when the 'starting torque is applied the starting mechanism is so organized that the pinion stands at or near the inboard end of the projecting portion of the shaft, While the cams 2O and studs 21 are located at the outboard end. In other words, the pinion is between the cam mechanism and the bearing 11 and so closel to the latter as to receive the maximum bracing effect. Consequently,

; though the surfaces are continued With increasing steepness a short distance beyond these points to provide a factor of safety. As shown, the cam surfaces have less curvature in the initial stages than in the terminal stages. and therefore have accelerative gradations of pitch steepness.

The studs stand initially at a. a, Where they engage the shoulders 22. When the operating unit is caused to rotate, as by clos- I ing a circuit to energize the starting motor,

the studs ride along the cam surfaces, which, in their initial stages, are so nearly at right angles to the axis of rotation that they do not develop enough torque to overcome the inertia of the transmission unit, but develop a powerful end-thrust and relatively slow axial movement of the transmission unit. `Before reaching points Where the steepness of pitch will develop enough torque to overcome the inertia of the transmission, the pinion will have been shifted into gear and will therefore be restrained from turning until the torque ,becomes sufficient to start the engine. During the latter stages of shifting the transthe axial movement of the transmission unit ceases When the gradually increasing steepness of the cam surfaces 20 and the gradually increasing resistance of the spring 16 have been compounded to a degree suiicient to n overcome the resistance of the engine. Even if the engine gear 15 did not turn at all the pins 21 would never reach the steepest parts of the cam surfaces because they continue With increasing steepness beyond the points Where the pins are arrested by the spring 16.l Thus, in every case the pins advance along the cams only to the points Where the start-,y

ing force is balanced by the engine load and the spring 16, and the construction does not include any shoulder or other positive abutment to arrest the axial movement of the transmission unit. This feature prevents all shock, even in extreme cases as when, for example, the startingmotor is arrested by a backfire or failure of the engine to respond to the starting force.

The spring 16, in addition to returning the transmission unit to its inoperative position, also modifies the angle of repose of the cam surfaces by bringing about a balance between the torque and the load sooner than if no spring resistance were applied to the transmission unit. As the end-thrust applied by the cam surfaces decreases the ycounterthrust applied by the spring increases, but in no case is the end-thrust transmitted to the starting motor when, as shown, the' abutment or backing for the spring 16 is provided by a shoulder on' the starting shaft 10. According to the construction shown the cam thrust and the counter-thrust of the spring are'both sustained by that portion of the shaft between the studs 21 and the shoulder behind the spring, each phase of the thrust counteracting the other. When the engine starts under an explosive impulse it causes the transmission unit of the starter tov overrun the operating unit, whereupon the spring 16 returns the transmission unit to its initial position as .shown in Figure 1.

I claim:

1. An engine starter comprising a rotatable and axially movable transmission unit including a starting pinion for engaging and disengaglng a gear of the engine, a rotatable operating unit arranged in cooperative relation to said transmission unit, one of said units having a curved cam surface of gradually increasing pitch andthe other having means to coact therewith to shift said pinion into gear, and a spring arranged to balance the end-thrust of said transmission unit so that said means will be prevented from adyancing to the steepest part of said cam surace.

2. An engine-starter comprising two telescopically related units of which the outer one is supported by the inner one and is provided With a starting pinion, one of said units including a cam and the other including means for coacting with said cam to shift the said outer unit axially and apply the starting torque thereto, and a 'spring arranged to react on said outer unit to arrest the axial movement thereof'and to develop the starting torque gradually to the maximum degree.

3. An engine starter comprising a supporting memberhaving a smooth cylindric external surface, a tubular transmission unit surrounding said supporting member and having a smooth cylindric internal surface bearing thereon and arranged to rotate and slide axially thereon, said transmission unit including a starting pinion for engaging and disengaging a gear of the engine, a spring arranged to urge said transmission unit endwise so as to maintain it normally in an inoperative position, and rotary operating means hav,-

ing diametrically opposite studs projecting radially, said transmission' unit having diametrically opposite twin,v cam surfaces arranged to coact with said studs respectively to shift said transmission unit to an operative position against the appliedstress ofsaid spring, said cam surfaces being curved so that ,the starting action will develop an initially powerful and gradually diminishing endthrust and a gradually increasing torque.

4. An .engine starter comprising a rotary operating unit having a smooth cylindric portion, an axially movable and rotary transmission unit surrounding and supported by said portion so as to slide and turn thereon, said transmission unit including a starting pinion Ifor engaging and disengaging an engine gear, one of said units having a radially projecting cylindric element and the other having a concave cam surface formed and arranged to coact with said element to shift said transmission unit axially to operative position With gradually increasing speed and torque and with gradually decreasing end thrust, and a spring arranged to arrest axial movement of said transmission unit when said radially projecting element is at an intermediate point of said cam surface.

5. An engine-starter comprising a rotary operating unit, an axially movable transmission unit arranged to slide and turn thereon and having a starting pinion for engaging and disengaging an engine gear, and a spring arranged to oppose With increasing force the axial movement of said transmission unit to starting position, one of said units having a cam surface arranged to cooperate with the other one of said units to shift the transmission unit to starting position against the applied force of said spring, and said cam surface being curved with gradually increasing steepness of pitch beyond a degree suiiicient to effect a starting operation.

I 6. An engine starter comprising a starting shaft provided with diametrically opposite operating lugs, a compression spring surrounding said shaft, an abutment for said spring, and a sleeve interposed between said 'spring and said lugs and arranged to slide 

